Journal of the Society of Motion Picture Engineers (1930-1949)

rence of field complaints. For this investigation the original full-view window engine (see Fig. 4) without the camera attachments was used. The ERPI camera was used again with 16mm Super XX motion picture film since photographs of consecutive explosions were again required. It was necessary in portions of this investigation that the angular position of the crankshaft for each photograph be known since the photographs were to be used in connection with pressure card data. A double-lobed cam was used on the distributor so that the spark plug (which was in the field of the camera) would fire twice, once to initiate combustion and again 90 crank-angle degrees later for a timing mark. These spark discharges did not always appear on the film because they would sometimes occur entirely during the twothirds of the time the film was not being exposed. By using the built-in ERPI timer and those spark discharges which were available, it was possible to determine the average time in crank-angle degrees per frame and so determine the angular position for each photograph. Similar calculations were made on the time axis of the pressure records so that the photographs and pressure records could be related. It is interesting to note that the speed of the engine could be found more accurately from the flame photographs than with the available engine instrumentation due to the electrical timer built into the ERPI. For orientation purposes the metal frame around the quartz window was illuminated with 120-w photoflood lamps. These lamps were used at shallow angles of incidence to the head of the engine so that the combustion chamber itself was not illuminated. This frame outline on each photograph provided the necessary reference points for the orientation of the random centers of ignition which occur during autoignition. In this autoignition investigation various types of engine deposits were accumulated with a full metal head on the engine. The engine was then stopped and the quartz head substituted for the metal one. Pictures of the combustion process in the presence of the deposits were taken shortly after the engine was restarted. Ordinarily the engine with the quartz head could be run for only short periods of time with deposits in the combustion chamber since the deposits became detached from the combustion chamber walls and were deposited on the quartz window. By taking photographs of consecutive explosions as they occurred in the presence of various deposits, some very important effects of combustion chamber deposits upon the combustion process were determined. Interest was again revived in the subject of autoignition in 1951 since autoignition rather than knock became one of the most important considerations in attempting to increase the performance of automobile engines. The original full-quartz-head window engine, now 21 years old, was again used at the beginning of this investigation which is now in progress. Four changes have been made in the procedure used in 1943. The first was the substitution of an Eastman Model III High-Speed Camera for the older ERPI camera. The basic principles of operation of the two cameras are the same but improved methods of operation are incorporated in the newer camera. A complete description of this camera may be found in the literature.6 Second, since stiffening blocks had been added to the top surface of the window frame, the angle of incidence of the illumination from the flood lamps used to light up the frame around the quartz window had to be increased. In so doing some of this light illuminated portions of the combustion chamber making definition of the combustion process in these areas difficult. There F. W. Bowditch: Research Photography 481